IF YOU GO

From Chattanooga, take Interstate 24 West to exit 155 for Jasper/state Highway 28 and continue north. Go 2.6 miles, then turn left on Mel Dixon Road (a sign directing spectators to the Trial Training Center is posted). Follow the signs on Betsy Pack Drive/Valley View Highway into the town of Sequatchie, Tenn. Go another mile to Coppinger Cove Road and follow signs to the center. Admission is $40 for the weekend, $20 per day for adults and $10 for children age 5-12. For more information, go to the TTC website, trialstrainingcenter.com or call 423-942-8688.

While two-wheeled competitors whiz almost silently through a Chattanooga road course this weekend, another world-class, bi-wheeled event will have competitors thundering up and down a treacherous Sequatchie Valley mountainside.

Fifty-five riders from 12 countries who will compete this weekend in the FIM Trials World Championship 2013 Wagner Cup started arriving Thursday and are practicing today at Sequatchie, Tenn.'s Trial Training Center course. The course is becoming known around the world for its beauty and technical difficulty, according to Ashley Jackson, one of the event organizers at the center.

FIM -- the Federation Internationale de Motocyclisme -- is the governing body of grand prix motorcycle racing, and this weekend's championship is the first in the U.S. in the last five years, officials said.

Some of the world's top trials riders will compete, including six-time world champion Toni Bou, of Spain, and four-time national U.S. champion Patrick Smage from Wisconsin, she said.

Competitive events start Saturday and continue through Sunday afternoon, but other activities begin this morning with sightseeing tours, an adventure ride, demonstrations, clinics and vendors, Jackson said. A concert Saturday night features the Collins Brothers Band.

Between 7,000 and 10,000 spectators are expected.

Noncompetitive activities continue through Monday afternoon, organizers said, and some special training is set for Tuesday with world-renowned trainer Eric Storz.

But it's the racing thousands of spectators will want to see, and that starts Saturday.

"The first rider goes out at 9:30 a.m. CDT and then every minute after that," Jackson said. The competition continues Sunday, with racing starting at 9:30 a.m.

Trials competitions are nothing new in motorcycle racing.

Riders tackling the course this weekend will be attacking a series of obstacles that require balance, strength and expert skills, said Dan Brown, owner of the center.

Spectators should bring comfortable walking shoes, sunscreen, a camera, a hat and, otherwise, no more than can be easily carried while changing locations, Brown said.

"The hills will be alive. There'll be some fantastic riding," he said. "They'll ride a motorcycle over things you wouldn't believe could be done."

KTM motorcycles factory rider Kyle Redmond, who raced in the 2012 Kenda Tennessee Knockout "Enduro-cross" event in Marion County last summer, described the center's terrain as "really, really tough" and "some of the hardest terrain you can ride."